Ethernet LAN Problem: 2 ISP, 1 router, 1 modem, 1 modem/router

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Subject Author Date
Problem: 2 ISP, 1 router, 1 modem, 1 modem/router citylight 09-20-06
Posted by citylight on September 20, 2006, 10:14 am
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Hello everyone.
I used to have only one ISP. A Cable Internet Connection with a
cable modem connected to a router, and the router connected to a 24
port switch. And the switch connected to about 20 computers.

Since the router is dual wan, i decided to add a second ISP(DSL)
as backup in case the other one is down. I planned to plug in the 2nd
ISP to the 2nd WAN port of the router in order to utilize the load
balancing feature of the router. And also I expected that the router
would automatically switch between the two ISP's, whichever is
available. Unfortunately, the 2nd ISP provided me with a modem/router.
They wouldnt allow me to configure the modem/router as a router only so
that i can plug it to 2nd WAN Port of my existing router.

Can I connect the modem/router to the 2nd WAN port of my existing
router without reconfiguring the modem/router as a modem only? Is there
any other way i can configure my setup so that the 20 computers can
access the internet as long as at least 1 ISP is available?

Im using Win XP Pro on all pc's.

Any help would be highly appreciated. Thanks in advance.


Posted by glen herrmannsfeldt on September 20, 2006, 1:51 pm
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(snip)
> Since the router is dual wan, i decided to add a second ISP(DSL)
> as backup in case the other one is down. I planned to plug in the 2nd
> ISP to the 2nd WAN port of the router in order to utilize the load
> balancing feature of the router. And also I expected that the router
> would automatically switch between the two ISP's, whichever is
> available. Unfortunately, the 2nd ISP provided me with a modem/router.
> They wouldnt allow me to configure the modem/router as a router only so
> that i can plug it to 2nd WAN Port of my existing router.

As an ethernet question, the consideration is whether you need
a crossover cable or a straight through cable. Most likely straight
though.

I don't see anything wrong with connecting the 2nd WAN port to
the DSL modem/router. I presume you will be on a NAT using private
addresses in any case. You do need to make sure that the appropriate
different (sub)net addresses are used on the two ports.

If you have more questions, this is really an IP question and should
go to comp.protocols.tcp-ip.

-- glen

Posted by citylight on September 21, 2006, 11:08 am
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glen herrmannsfeldt wrote:
> (snip)
> > Since the router is dual wan, i decided to add a second ISP(DSL)
> > as backup in case the other one is down. I planned to plug in the 2nd
> > ISP to the 2nd WAN port of the router in order to utilize the load
> > balancing feature of the router. And also I expected that the router
> > would automatically switch between the two ISP's, whichever is
> > available. Unfortunately, the 2nd ISP provided me with a modem/router.
> > They wouldnt allow me to configure the modem/router as a router only so
> > that i can plug it to 2nd WAN Port of my existing router.
>
> As an ethernet question, the consideration is whether you need
> a crossover cable or a straight through cable. Most likely straight
> though.
>
> I don't see anything wrong with connecting the 2nd WAN port to
> the DSL modem/router. I presume you will be on a NAT using private
> addresses in any case. You do need to make sure that the appropriate
> different (sub)net addresses are used on the two ports.
>
> If you have more questions, this is really an IP question and should
> go to comp.protocols.tcp-ip.
>
> -- glen

Thank, I will try that. :)


Posted by citylight on October 12, 2006, 5:52 am
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glen herrmannsfeldt wrote:
> (snip)
> > Since the router is dual wan, i decided to add a second ISP(DSL)
> > as backup in case the other one is down. I planned to plug in the 2nd
> > ISP to the 2nd WAN port of the router in order to utilize the load
> > balancing feature of the router. And also I expected that the router
> > would automatically switch between the two ISP's, whichever is
> > available. Unfortunately, the 2nd ISP provided me with a modem/router.
> > They wouldnt allow me to configure the modem/router as a router only so
> > that i can plug it to 2nd WAN Port of my existing router.
>
> As an ethernet question, the consideration is whether you need
> a crossover cable or a straight through cable. Most likely straight
> though.
>
> I don't see anything wrong with connecting the 2nd WAN port to
> the DSL modem/router. I presume you will be on a NAT using private
> addresses in any case. You do need to make sure that the appropriate
> different (sub)net addresses are used on the two ports.
>
> If you have more questions, this is really an IP question and should
> go to comp.protocols.tcp-ip.
>
> -- glen

Many, many thanks sir. I got it working now. I connected the
modem/router to the 2nd wan port. Assigned a static IP to 2nd Wan, with
the Lan IP of modem/router as gateway. Thanks again.


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